yes, the github contributions heatmap is known to be open for manipulation. folks will use it to draw art by backdating commits.

if i have it right, only commits can be manipulated, other contributions should be safe — i don't know what is possible for orgs moving old discussion archives into github, see python's issues for reference

see: https://github.com/dspinellis/unix-history-repo

They're almost certainly not genuine accounts, maybe used for karma farming, phishing, social engineering, future malware distribution?